This invention relates to a package structure made from a thermoplastic resin and having a cavity to hold semiconductor elements such as diodes, transistors, etc, or integrated circuits of these semiconductors (hereinafter referred to as "a semiconductor") airtightly.
As packaging methods for semiconductors, there is mainly used a plastic package method wherein lead frames previously mounting a semiconductor are placed between top and bottom molds and a molten resin is poured into a cavity formed by these molds. But according to this method, since the semiconductor is forced to be placed in a high pressure and high temperature state due to a direct contact with the molten resin, there sometimes takes place cutting of wires connecting lead terminals and electrodes of the semiconductor.
In order to improve such a defect of the plastic package method, there is proposed a method wherein lead frames mounting a semiconductor are inserted between a pair of resin moldings having a cavity therein and integrally joined (Japanese Patent Unexamined Publication No. 98969/76). But even in this method, since the semiconductor is in a state of hanging in a closed space, there are problems in that the dissipation of heat from the semiconductor is difficult at the time of operation, thermal resistance becomes larger particularly in the case of semiconductor with higher integration capacity. Further, since a tab of lead frame for fixing the semiconductor is only supported by two tab hanger 9 as shown in FIG. 3 in usual, wires which connect electrodes of semiconductors and lead terminals are deformed or cut due to thermal deformation of the tab hangers when subjected to a heat cycle test.